Quote Originally Posted by nsherry61 View Post
Contrary to suggestions above, a space blanket, either under or on top of your sleeping pad, only reflects infrared radiation...
A non permeable aluminized mylar space blanket does NOT only work to add warmth to a sleep system by reflecting infrared radiation. It also works to add heat by reducing or eliminating convective and evaporative heat losses. If one does not mind the shininess letting it be the ground sheet or over cover choice it can work better to add warmth to a ground based sleep system(I guess it can be used in hangs too providing the slipperiness factor isn't an issue?) than the various forms of Tyvek. However, again it is non permeable and like Tyvek high dryer heat shrinks it. It also does not pill or break down it's water resistance as Tyvek does with use. It also tends to attract less debris as Tyvek does particularly after some Tyvek usage. I see it as gear piece that's cheap, somewhat more durable, readily available, easy to incorporate, UL in wt, UL in packed volume, and diverse in its usage in sleep systems and beyond. Many times I have draped an aluminized sheet over me as a mid layer apparel piece. It reflects in sun as a S&R survival piece as well. It is not a shoulder season stand alone replacement for an insulated pad though.